[llvm] Migrate llvm::make_unique to std::make_unique

Now that we've moved to C++14, we no longer need the llvm::make_unique
implementation from STLExtras.h. This patch is a mechanical replacement
of (hopefully) all the llvm::make_unique instances across the monorepo.

llvm-svn: 369013
diff --git a/llvm/tools/llvm-exegesis/lib/Target.cpp b/llvm/tools/llvm-exegesis/lib/Target.cpp
index 945aabb..a5ba24c 100644
--- a/llvm/tools/llvm-exegesis/lib/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/Target.cpp
@@ -68,22 +68,22 @@
 
 std::unique_ptr<SnippetGenerator>
 ExegesisTarget::createLatencySnippetGenerator(const LLVMState &State) const {
-  return llvm::make_unique<LatencySnippetGenerator>(State);
+  return std::make_unique<LatencySnippetGenerator>(State);
 }
 
 std::unique_ptr<SnippetGenerator>
 ExegesisTarget::createUopsSnippetGenerator(const LLVMState &State) const {
-  return llvm::make_unique<UopsSnippetGenerator>(State);
+  return std::make_unique<UopsSnippetGenerator>(State);
 }
 
 std::unique_ptr<BenchmarkRunner> ExegesisTarget::createLatencyBenchmarkRunner(
     const LLVMState &State, InstructionBenchmark::ModeE Mode) const {
-  return llvm::make_unique<LatencyBenchmarkRunner>(State, Mode);
+  return std::make_unique<LatencyBenchmarkRunner>(State, Mode);
 }
 
 std::unique_ptr<BenchmarkRunner>
 ExegesisTarget::createUopsBenchmarkRunner(const LLVMState &State) const {
-  return llvm::make_unique<UopsBenchmarkRunner>(State);
+  return std::make_unique<UopsBenchmarkRunner>(State);
 }
 
 void ExegesisTarget::randomizeMCOperand(